Innovative non-toxic exfoliation of bulk g-C3N4 into ultra-thin 1D/2D nanosheets and nanotubes for accelerated sunlight-driven photocatalysis

Abstract

A relatively green and safer in situ H₂O₂-mediated solvothermal technique has been employed to significantly enhance the photocatalytic activity of bulk g-C₃N₄ (bulk CN). This novel approach generates free oxygen (O₂), facilitating simultaneous exfoliation and heteroatom doping of bulk CN. As a result, the optoelectronic and physicochemical properties of g-C₃N₄ are synergistically improved. The morphological transformation of bulk CN from thick multilayered structures to 2D ultrathin nanosheets and 1D nanotubes improves its discrete band structure, enhances its pore network and specific surface area, and facilitates the separation of photoexcited charge carriers. The 48 h exfoliated CN (CN-48) exhibits a significantly enhanced photocurrent response (447%) compared to bulk CN, along with a longer lifetime of photogenerated charge carrier separation. Furthermore, electrochemical impedance spectroscopy (EIS) reveals that CN-48 has a lower charge transfer resistance (R_ct) than bulk CN, confirming its superior charge transport efficiency. Accordingly, CN-48 exhibited 220% and 180% higher degradation rates for Congo red (CR) and tetracycline (TC), respectively, compared to bulk CN. Furthermore, CR and TC degradation efficiencies were enhanced by increasing the pH and decreasing pollutant concentrations. The total organic carbon/chemical oxygen demand (TOC/COD) was effectively reduced by 80% and 74% following the degradation of 50 mg L⁻¹ of CR and TC, respectively. Additionally, CN-48 demonstrated sustained degradation efficiencies of 98% for CR and 93% for TC over five consecutive cycles. This innovative exfoliation method is both facile and eco-friendly, providing a practical and scalable approach to significantly enhance photocatalytic activity under sunlight compared to existing exfoliation techniques.